1. Field of the Invention
This invention relates to an additive for a heat-sensitive recording material, more specifically an additive for use (in a heat-sensitive recording layer of a heat-sensitive recording material) utilizing the reaction of a colorless or slightly colored basic dye with a (developer capable of producing a color on contact with the dye) to a heat-sensitive recording material containing the additive, and to a method for the production of the heat-sensitive recording material.
2. Prior Art Statement
The heat-sensitive recording material which comprises a sheetlike substrate (such as paper or polyester sheet), a heat-sensitive recording layer superposed on the substrate and composed of a basic dye and a developer capable of reacting with and coloring the dye on exposure to heat, and optionally a surface-protecting layer formed on the heat-sensitive recording layer has been finding extensive utility in various heat-sensitive recording devices such as heat-sensitive facsimile systems, heat-sensitive printer, etc. Recent years have seen rapid improvement, diversification, and performance enhancement of heat-sensitive recording devices. As a result, increasing demand has arisen for higher quality heat-sensitive recording materials, particularly for materials with high sensitivity usable for high-speed recording.
Numerous proposals have been made as to the combined use of heat-fusible substances (such as fatty acid amides, oils, and fats) as an additive aimed at enhancing the sensitivity of heat-sensitive recording materials. However the enhancement of recording sensitivity entails new drawbacks such as lower stability of the heat-sensitive recording layer, degradation of whiteness of the recording layer, and none of the heat-fusible substances proposed to date for the combined use has enabled production of a satisfactory heat-sensitive recording material.